IC Support Bracket
Another advantage of making a slot out of the hole is if you get an raised SC top that changes the angle of the tube to the point that it changes the alignment of the tube at the IC. The slot will allow you to reposition the tube and still get the support whereas without slotting it, the bolt will not fit back on and that will allow to much vibration which makes the IC bolts or the spanner nut to work their way loose. And that will cause bad idle, detonation or other problems. Good Luck